Latices of vinylidene chloride interpolymers thickened with ethylenemaleic anhydride copolymer and article coated therewith



United. States Patent I. 1 i 51; s. 'LATIC S. QE v YL N oHLo D I ER- PGLYMERS THICKENED QWITH ETHXLENE- Z MALEICADUIXDBIDECOPOLYMER AND ARTI- ..C E.C ATE TH REW T 1 Leonjli unir," roux, Francis W. Michelotti, Brooklyn, 3 Sebastian T. Brancato, Q'uensVillage, and Alice W.

Puck1iat,-New York, N.Y., assigriors to Interchemical iCorpor'atioh', NewYork, N.'Y., a corporation of Ohio No Drawing. Fileg l Aug.f31, ,122, Ser. No. 220,872

, I a IZClaims. (Cl..2602.6)

This" i t/ethos relates ta raises qr vin'ylidene chloride seria -mg their diminishes. Application at solution coatkings to p'o'r throughf'me and the polymer into" or even through theweb, thus caus- 'ing discontinuity in the coating film andsometimes discoloration on the reverse surface. ln'ifall cases the use of organic solvents has the .known disadvantages of expense, fiammability,"odor; and sometimes toxic vapors.

By using latices comprising dispersions of high polymaterials is ofteh accompanied by fstrike tr ers in water, it-.is..possible to overcome some of. the

undesirable pr pertiesfof polyi ner solutions? Organic solvents awa t eby dispensed with and polymers of high molecular weight .mavbeapplied'. Furthermore, emulsion techniques avoid. the eirpehseof isolating the polymers as] .the polymerizationsysterrr, ln' emulsion polymerize p thermal cohtro'l is,;comparatively (easy, each s-mall.particle beihgsurfrourided by water, also the lmoderate visco sity allows good heat transfer to the kettle jacket... Rolynier s" or, high molecular weight can thus :be obtained.,with amuch shorter-reaction time than by bulk polymerization, the difference being a few. hours versus a few days.

When the qcontinuousphase .of such an emulsion is in substantial excess, the viscosity of the emulsion is 1gu'iides'ired penetration oft-the solvent.

up of the emulsion.

ice 7 Conditions of storage, including high and low temperatures,.agitation and vibration, dilution or evaporation, all may play their part in changing the properties and-make- V The same factors may also come into .play during. coating operations. The stability, in fact, is determined'by almost all factors involved in the formulation and preparation of an emulsion. The

viscosity of an emulsion may often be lowered by in.-

creasing the ratio of the continuous phase to the disperse phase. Similarly it may often be increased by decreasing Increase in viscosity also may, be brought this ratio. about by addition ofthickene'rs suchas soap gels, lipophilic fatty acid ester, gums, or alumina gel to the continuous phase. The reduction of clumping or of particle size often has the same effect. The introduction of air bubbles as a third phase has a .tende'ncyto increase the viscosity, but such a procedure must be used with caution 7 since such systems maybe quite unstable.

essentially that of the liquidf As the amount of dis-:

; continuous phaseincreases, the viscosity increases .iuntil the emulsion no longer fiows. At the point where the phase, the crowding together of thelparticles produces trical charges, lubricanthfilms'on the particles, etc. beeonieimportant. Theoretically, the'maxirrium volume Although some emulsions may be sider abl e distortiori' the squeezed-togethef particles I v at ftlie'sefhigh ratio's re'sultsf ;E riiulsiorijVi s cosity often 3 changes withag', so etir'nes owing to otropic actidm a structural viscosity component in .the overall apparent, viscosity; Under these" circumstances particle "size, 'elecresin in dimethyl formamide at 25 c. The similar 7 ethylene-maleic-anhydride"copolymer, also known as;

.DX-840-31, is equally good provided it is first hydrolone coating is applied.

Although these general lines of attack are known, the actual tailoring ofan emulsion to fit a number of requirements, some unrelated to one another, is very difficult and sometimes seemingly impossible. The imparting of one desirable property may entrain the impairment of other desirable properties. The methods of altering vis-' cosity mentioned above, whilequalitatively correct, may produce-such small. changes that no practical end is achieved. Each particular emulsion; presents a new problem.

0n non-porous substrates such as glassine, Mylar, cellophane, and other flexible, packaging films there is a decided tendency for. unthickenedlatices to ex- 'cessively' and even crawl without wetting the substrate. The thickened latices of the present inventioncompletely overcome this tendency andiilm' having the ,desired 'propertiesis obtained. Furthermore, multiple coats may be applied with complete drying between each application. This is not possible with unthickened or inadequately thickened latices, which exhibit crawling when more than 'The prefer-red latices of this invent-ion are prepared by redox emulsion polymerization of about 80% to 87% by weight of vinylidene-chloride,about 9% to 18% V weight of methacrylic acid the solid content being about v of 0.6 to 27% parts by Weight, based on the weight j of latex solids; The preferredthickener is a linear ethyl- "ene-maleic acid copolymer of high molecular weight having the recurrent group a volume of the internal phase exceeds that of the external 7 40%60% byweight. Thickener is added to the amount cosity is 1.0 when determined on a 1% solution of the ly /ed to the' acid form. {Hydrolysis is conveniently carried out by heating aslurry of the solid in-water 10-15 suitable method of'hydrolysis may als'o be used. -The V addition of these thickeners did not increase the moisture vapor transmissionrate over that of the unthickened .I'ninutes at C. and cooling thesolutionl' ;Any other laticesin cured film io'r-rn. Their resistance to'moisture transmission is at least as high as' that of the best: prior ,f'art films." fj V l r V Other thickeners, such as ,(a)" ammonia, ;(b) the sodium s'alt of carboxymethyl cellulose, also known .as

Cellulose Gum, hydroxy ethyl cellulose, also known as Cellosize, (d) polyethylene oxide gum, also known as Polyox, (e) the polymer produced by reacting 100 parts by weight of acrylic acid with 1 to 2 parts by Weight of allyl sucrose (containing 5.6-5.8 allyl groups per molecule), also known as Carbopol 934, (1) linear maleic anhydride copolymers of lower molecular weights than DX84031, either hydrolyzed or unhydrolyzed, (g) crosslinked ethylene-maleic anhydride copolymers of various molecular weights, (h) crosslinked ethylenemaleic acid copolymers of lower molecular weights than DX-840-32, (i) crosslinked ammonium-amide forms of ethylene-maleic acid copolymers of various molecular weights, (j) linear ammonium-amide forms of ethylenemaleic acid copolymers of various molecular weights, (k) linear ethylene-maleic acid copolymers of various molecular weights, (l) methyl cellulose, and (m) carboxymethyl hydroxyethyl cellulose were unsuccessful owing to incompatibility, poor thickening, or increase in water vapor transmission rate.

Example 1500 g. water, 40 g. Duponol C, 6 g. ammonium persulfate, 212.5 g. vinylidene chloride, 27.5 g. ethyl acrylate, and g. methacrylic acid were heated to C. 3 g. sodium metabisulfite were then added and the mixture refluxed at 36 C. 637.5 g. vinylidene chloride, 82.5 g. ethyl acrylate, and 30 g. methacrylic acid were added dropwise over a period of 1% hours, the temperature being kept at 38 C. After the addition, the temperature was raised to C. The material was then cooled and filtered. It had a solids content of 41.3%

latex was superior to the unthickened latex in being easier to apply to paper, etc., giving a more uniform film free from craters or pinholes, and having less strike-in. It also had better clarity than any commercially available vinylidene chloride latex examined.

Incorporation of /2-3% by weight of a Carbowax, based on the weight of resin solids, increased the stability of the latices at least 10%.

One drawback of all the foregoing embodiments of this invention is the fact that when aluminum or various steels are in contact with the above latices, appreciable corrosion is observed to have taken place within 2 to 3 hours. Surprisingly, such corrosion can be effectively prevented by incorporating up to about 2% by weight, based on resin solids, of ethylenediamine tetraacetic acid (EDTA) in the latices. For example, aluminum and various steels that showed appreciable corrosion after by weight. The latex was thickened to a value .of 300 centipoises with a 10% solution of DX-840-32. 2% by weight of solid DX-840-32, based on the latex solids was required.

The preferred type of thickened latex showed changes in viscosity when aged over a week, but shielding it from ultraviolet radiation, for instance by storing in amber bottles, improved the aging stability somewhat.

Considerable improvement in stability was attained by distributing the Duponol C proportionately between the initial charge inthe flask and the material added dropwise. The solids content was varied from about 40% to about 60%. The example above thus was varied by having only 10 g. of Duponol C in the original charge, the other 30 g. being mixed with the monomers that were added dropwise. It was also found that sodium lauryl sulfate was more effective than many other commercial emulsifiers tried such as Brij 35 Triton X-205, "Triton X-305, "Triton X-405, Aerosol OT, Tergi- Triton X-200, Tergitol XD, Tergitol 08, Onyx 132 D, Garfac RE 610, Garfac RM 710," Garfac GB 520, Garfac L0 529, Triton, 770 conc., Garfac PE 510, Garfac RM 510, and OPE-70. Duponol C is sodium lauryl sulfate.

tel NPX, Hyamine 1622, Duponol ME, Brij 30,

The latices of the present invention displayed an unusual number of desirable properties and were thus found to be superior over the prior art latices used for the same type of applications. Cured films made therefrom had superior impermeability to water vapor and gases, a feature of considerable importance commercially. In packaged goods, it is often desirable to prevent access of air and loss (or gain) of moisture. The films also imparted good grease proofing, even on scored areas. They had excellent flexibility and resistance to blocking. Adhesion to non-porous substrates was outstanding. They are therefore of particular value 1 in coating food packaging materials.

Coatings may be applied by conventional methods .such as reverse roller coating. They may be cured simply by air drying but, since speed is generally desirable, heating is preferable. At 300 R1 minute is sufiicient and at 150 F, 10 minutes are required. The thickened 2 to 3 hours contact with the latices, showed negligible, if any, corrosion after 336. hours contact with the same latices to which 1% by weight of EDTA, based on resin solids, had been added. The latices containing EDTA have a pH value of 2.0, thus their greatly decreased corrosive effect is totally unexpected.

Carbowax is a poly (ethylene ether) glycol. The preferred types are those having molecular weights in the range 300-1500. v

What is claimed is: 1. A coating composition comprising a thickened 1atex consisting essentially of an aqueous dispersion of an interpolymer made from about to about 87% by weight of vinylidene chloride, about 9% to about 18% by weight of ethyl acrylate, and about 1% to 4% by weight of methacrylic acid, the latex containing about 0.6 to 2.7 parts by weight, based on the latex solids, of a thickener consisting of a linear ethylene-maleic acid copolymer having the recurrent group.

-ECHg-CH7-CHg-(3Hz OOH 0011 and having a specific viscosity of 1.0 when determined on a 1%-by-weight solution of the copolymer in dimethyl formamide at 25 C., the solids content of the latex being about 40% to about 60% by weight.

2. A coating composition comprising a thickened latex consisting essentially of an aqueous dispersion of an interpolymer made from about by weight of vinylidene chloride, about 11% by weight of ethyl acrylate, and about 4% by weight of methacrylic acid, the latex containing about 2% by weight, based on the latex solids, of a thickener consisting'of a linear ethylene-maleic acid copolymer having the recurrent group 00H OOH and having a specific viscosity of 1.0 when determined on a 1%-by-weight solution of the copolymer in dimethyl formamide at 25 C., the solids content of the latex being about 50% by weight.

3. A mixture of the coating composition of claim 1 and /2 to 2% by weight, based on the weight of resin solids, of ethylenediamine tetraaoetic acid.

4. A mixture of the coating composition of claim 2 and M: to 2% by weight, based on the weight of resin solids, of ethylenediamine tetraacetic acid.

5. A mixture of the coating composition of claim 3 and /2 to 3% by weight, based on the weight of resin solids, of poly (ethylene ether) glycol.

6. A mixture of the coating composition of claim 4 and /2 to 2%, by weight, based on the weight of resin solids, of poly(ethylene ether) glycol.

7. v A' non-metallic substrate having coated thereon a film comprising the cured coatin g composition of claim 1.

8. A non-metallic substrate having coated .thereon a 9. A non-metallic substrate having coated thereon a film comprising the cured coating composition of claim 3. 10. A non-metallic substrate having coated thereon a film comprising the cured coating composition of claim 4. 11. A non-metallic substrate having coated thereon a film comprising the cured coating composition of claim 5. 12. A non-metallic substrate having coated thereon a film comprising the cured coating composition of claim 6.

6 V References Cited in the file of this patent UNITED STATES PATENTS Grenley et a1 June 24, 1958 OTHER REFERENCES Monsanto Product Information Bulletin No. 1066, Water Soluble Copolymers of Ethylene Maleic Anhydride, 1959 (pages 1, 5, and 8 relied upon). 

1. A COATING COMPOSITION COMPRISING A THICKENED LATEX CONSISTING ESSENTIALLY OF AN AQUEOUS DISPERSION OF AN INTERPOLYMER MADE FROM ABOUT 80% TO ABOUT 87% BY WEIGHT OF VINYLIDENE CHLORIDE, ABOUT 9% TO ABOUT 18% BY WEIGHT OF ETHYL ACRYLATE, AND ABOUT 1% TO 4% BY WEIGHT OF METHACRYLIC ACID, THE LATEX CONTAINING ABOUT 0.6 TO 2.7 PARTS BY WEIGHT, BASED ON THE LATEX SOLIDS, OF A THICKENER CONSISTING OF A LINEAR ETHYLENE-MALEIC ACID COPOLYMER HAVING THE RECURRENT GROUP. 